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Some of the major misconceptions in the United States about climate change—such as the focus on scientific uncertainty, the “debate” over whether climate change is caused by humans, and pushback about how severe the consequences might be—can be seen as communications battles. An interesting area within communications is the contrasting use of guilt and shame for climate-related issues. Guilt and shame are social emotions (along with embarrassment, pride, and others), but guilt and shame are also distinct tools. On the one hand, guilt regulates personal behavior, and because it requires a conscience, guilt can be used only against individuals. Shame, on the other hand, can be used against both individuals and groups by calling their behavior out to an audience. Shaming allows citizens to express criticism and social sanctions, attempting to change behavior through social pressure, often because the formal legal system is not holding transgressors accountable. Through the use of guilt and shame we can see manifestations of how we perceive the problem of climate change and who is responsible for it. For instance, in October 2008, Chevron, one of the world’s largest fossil fuel companies, placed advertisements around Washington, DC, public transit stops featuring wholesome-looking, human faces with captions such as “I will unplug things more,” “I will use less energy,” and “I will take my golf clubs out of the trunk.” Six months later, DC activists reworked the slogans by adding to each the phrase “while Chevron pollutes.” This case of corporate advertising and subsequent “adbusting” illustrates the contrast between guilt and shame in climate change communication. Guilt has tended to align with the individualization of responsibility for climate change and has been primarily deployed over issues of climate-related consumption rather than other forms of behavior, such as failure to engage politically. Shame has been used, largely by civil society groups, as a primary tactic against fossil fuel producers, peddlers of climate denial, and industry-backed politicians.
Hail has been identified as the largest contributor to insured losses from thunderstorms globally, with losses costing the insurance industry billions of dollars each year. Yet, of all precipitation types, hail is probably subject to the largest uncertainties. Some might go so far as to argue that observing and forecasting hail is as difficult, if not more difficult, than is forecasting tornadoes. The reasons why hail is challenging are many and varied and reflected by the fact that hailstones display a wide variety of shapes, sizes and internal structures. There is also an important clue in this diversity—nature is telling us that hail can grow by following a wide variety of trajectories within thunderstorms, each having a unique set of conditions. It is because of this complexity that modeling hail growth and forecasting size is so challenging. Consequently, it is understandable that predicting the occurrence and size of hail seems an impossible task.
Through persistence, ingenuity and technology, scientists have made progress in understanding the key ingredients and processes at play. Technological advances mean that we can now, with some confidence, identify those storms that very likely contain hail and even estimate the maximum expected hail size on the ground hours in advance. Even so, there is still much we need to learn about the many intriguing aspects of hail growth.
Throughout history human societies have been shaped and sculpted by the weather conditions that they faced. More than just the physical parameters imposed by the weather itself, how individuals, communities, and whole societies have imagined and understood the weather has influenced many facets of human activity, from agriculture to literary culture. Whether through direct lived experiences, oral traditions and stories, or empirical scientific data these different ways of understanding meteorological conditions have served a multitude of functions in society, from the pragmatic to the moral.
While developments made in the scientific understanding of the atmosphere over the last 300 years have been demonstrably beneficial to most communities, their rapid onset and spread across different societies often came at the expense of older ways of knowing. Therefore, the late 20th century turn to emphasizing the importance of and interrogating and incorporating of traditional ecological knowledge within meteorological frameworks and discourses was essential. This scholarly research, underway across a number of disciplines across the humanities and beyond, not only aides the top-down integration and reach of mitigation and adaptation plans in response to the threat posed by anthropogenic climate change; it also enables the bottom-up flow of forgotten or overlooked knowledge, which helps to refine and improve our scientific understanding of global environmental systems.
Charles A. Doswell III
Convective storms are the result of a disequilibrium created by solar heating in the presence of abundant low-level moisture, resulting in the development of buoyancy in ascending air. Buoyancy typically is measured by the Convective Available Potential Energy (CAPE) associated with air parcels. When CAPE is present in an environment with strong vertical wind shear (winds changing speed and/or direction with height), convective storms become increasingly organized and more likely to produce hazardous weather: strong winds, large hail, heavy precipitation, and tornadoes.
Because of their associated hazards and their impact on society, in some nations (notably, the United States), there arose a need to have forecasts of convective storms. Pre-20th-century efforts to forecast the weather were hampered by a lack of timely weather observations and by the mathematical impossibility of direct solution of the equations governing the weather. The first severe convective storm forecaster was J. P. Finley, who was an Army officer, and he was ordered to cease his efforts at forecasting in 1887. Some Europeans like Alfred Wegener studied tornadoes as a research topic, but there was no effort to develop convective storm forecasting.
World War II aircraft observations led to the recognition of limited storm science in the topic of convective storms, leading to a research program called the Thunderstorm Product that concentrated diverse observing systems to learn more about the structure and evolution of convective storms. Two Air Force officers, E. J. Fawbush and R. C. Miller, issued the first tornado forecasts in the modern era, and by 1953 the U.S. Weather Bureau formed a Severe Local Storms forecasting unit (SELS, now designated the Storm Prediction Center of the National Weather Service). From the outset of the forecasting efforts, it was evident that more convective storm research was needed. SELS had an affiliated research unit called the National Severe Storms Project, which became the National Severe Storms Laboratory in 1963. Thus, research and operational forecasting have been partners from the outset of the forecasting efforts in the United States—with major scientific contributions from the late T. T. Fujita (originally from Japan), K. A. Browning (from the United Kingdom), R. A. Maddox, J. M. Fritsch, C. F. Chappell, J. B. Klemp, L. R. Lemon, R. B. Wilhelmson, R. Rotunno, M. Weisman, and numerous others. This has resulted in the growth of considerable scientific understanding about convective storms, feeding back into the improvement in convective storm forecasting since it began in the modern era. In Europe, interest in both convective storm forecasting and research has produced a European Severe Storms Laboratory and an experimental severe convective storm forecasting group.
The development of computers in World War II created the ability to make numerical simulations of convective storms and numerical weather forecast models. These have been major elements in the growth of both understanding and forecast accuracy. This will continue indefinitely.
A typhoon is a highly organized storm system that develops from initial cyclone eddies and matures by sucking up from the warm tropical oceans large quantities of water vapor that condense at higher altitudes. This latent heat of condensation is the prime source of energy supply that strengthens the typhoon as it progresses across the Pacific Ocean. A typhoon differs from other tropical cyclones only on the basis of location. While hurricanes form in the Atlantic Ocean and eastern North Pacific Ocean, typhoons develop in the western North Pacific around the Philippines, Japan, and China.
Because of their violent histories with strong winds and torrential rains and their impact on society, the countries that ring the North Pacific basin—China, Japan, Korea, the Philippines, and Taiwan—all often felt the need for producing typhoon forecasts and establishing storm warning services. Typhoon accounts in the pre-instrumental era were normally limited to descriptions of damage and incidences, and subsequent studies were hampered by the impossibility of solving the equations governing the weather, as they are distinctly nonlinear. The world’s first typhoon forecast was made in 1879 by Fr. Federico Faura, who was a Jesuit scientist from the Manila Observatory. His brethren from the Zikawei Jesuit Observatory, Fr. Marc Dechevrens, first reconstructed the trajectory of a typhoon in 1879, a study that marked the beginning of an era. The Jesuits and other Europeans like William Doberck studied typhoons as a research topic, and their achievements are regarded as products of colonial meteorology.
Between the First and Second World Wars, there were important contributions to typhoon science by meteorologists in the Philippines (Ch. Deppermann, M. Selga, and J. Coronas), China (E. Gherzi), and Japan (T. Okada, and Y. Horiguti). The polar front theory developed by the Bergen School in Norway played an important role in creating the large-scale setting for tropical cyclones. Deppermann became the greatest exponent of the polar front theory and air-masses analysis in the Far East and Southeast Asia.
From the end of WWII, it became evident that more effective typhoon forecasts were needed to meet military demands. In Hawaii, a joint Navy and Air Force center for typhoon analysis and forecasting was established in 1959—the Joint Typhoon Warning Center (JTWC). Its goals were to publish annual typhoon summaries and conduct research into tropical cyclone forecasting and detection. Other centers had previously specialized in issuing typhoon warnings and analysis. Thus, research and operational forecasting went hand in hand not only in the American JTWC but also in China (the Hong Kong Observatory, the Macao Meteorological and Geophysical Bureau), Japan (the Regional Specialized Meteorological Center), and the Philippines (Atmospheric, Geophysical and Astronomical Service Administration [PAGASA]). These efforts produced more precise scientific knowledge about the formation, structure, and movement of typhoons. In the 1970s and the 1980s, three new tools for research—three-dimensional numerical cloud models, Doppler radar, and geosynchronous satellite imagery—provided a new observational and dynamical perspective on tropical cyclones. The development of modern computing systems has offered the possibility of making numerical weather forecast models and simulations of tropical cyclones. However, typhoons are not mechanical artifacts, and forecasting their track and intensity remains an uncertain science.
Pieter Maeseele and Yves Pepermans
The idea of climate change inspires and reinforces disagreements at all levels of society. Climate change’s integration into public life suggests that there is no evident way of framing and tackling the phenomenon. This brings forward important questions regarding the role of ideology in mediated public discourse on climate change. The existing research literature shows that five ideological filters need to be taken into account to understand the myriad ways in which ideology plays a role in the production, representation, and reception of climate change in (news and entertainment) media: (i) economic factors, (ii) journalistic norms, (iii) political context, (iv) ideological cultures, and (v) citizen decoding. Furthermore, two different interpretations of how ideology precisely serves as a filter of social reality underlie this literature: an interpretation of ideology as an independent variable, on the one hand, and as a constitutive practice, on the other. Moreover, these interpretations underlie a broader discussion in the social sciences on the relation between climate change and ideology and how scholars and activists should deal with it. By considering climate change as a post-ideological issue, a first perspective problematizes the politicization of climate change and calls for its depoliticization to foster consensus and public engagement. In response, a second perspective takes aim against the post-politicization and post-democratization of climate change (resulting from the adoption of the first perspective) for suppressing the role of ideology and, as a result, for stifling democratic debate and citizenship with regard to the climate issue. This latter perspective is in need of further exploration in future research, especially with regard to the concepts of ideological fault lines, ideological hegemony, and ideological strategies.
Among the factors that influence news decisions relative to climate change, journalistic background, professional norms, and culture are particularly important. There is empirical evidence that conservative journalists and media outlets are less likely to support the scientific consensus on climate change and more likely to promote climate change contrarianism.
Journalists with less expertise on climate change may produce less accurate coverage, investigative journalists may be more critical towards science, and journalists with a positive attitude towards the subject of climate change may make it more salient in the news.
There is also indication that climate journalists abandon the norm of balance and increasingly employ strategies of novelty, dramatization, personalization, and localization. The climate journalists also tend to synchronize their coverage to the policies of their governments.
Finally, journalists from the interpretive community around the IPCC or from science-friendly cultures are more likely to support the consensus on climate change, while journalists from collectivist cultures are more likely to endorse binding international agreements.
The Sahel of Africa has been identified as having the strongest land–atmosphere (L/A) interactions on Earth. The Sahelian L/A interaction studies started in the late 1970s. However, due to controversies surrounding the early studies, in which only a single land parameter was considered in L/A interactions, the credibility of land-surface effects on the Sahel’s climate has long been challenged. Using general circulation models and regional climate models coupled with biogeophysical and dynamic vegetation models as well as applying analyses of satellite-derived data, field measurements, and assimilation data, the effects of land-surface processes on West African monsoon variability, which dominates the Sahel climate system at intraseasonal, seasonal, interannual, and decadal scales, as well as mesoscale, have been extensively investigated to realistically explore the Sahel L/A interaction: its effects and the mechanisms involved.
The Sahel suffered the longest and most severe drought on the planet in the 20th century. The devastating environmental and socioeconomic consequences resulting from drought-induced famines in the Sahel have provided strong motivation for the scientific community and society to understand the causes of the drought and its impact. It was controversial and under debate whether the drought was a natural process, mainly induced by sea-surface temperature variability, or was affected by anthropogenic activities. Diagnostic and modeling studies of the sea-surface temperature have consistently demonstrated it exerts great influence on the Sahel climate system, but sea-surface temperature is unable to explain the full scope of the Sahel climate variability and the later 20th century’s drought. The effect of land-surface processes, especially land-cover and land-use change, on the drought have also been extensively investigated. The results with more realistic land-surface models suggest land processes are a first-order contributor to the Sahel climate and to its drought during the later 1960s to the 1980s, comparable to sea surface temperature effects. The issues that caused controversies in the early studies have been properly addressed in the studies with state-of-the-art models and available data.
The mechanisms through which land processes affect the atmosphere are also elucidated in a number of studies. Land-surface processes not only affect vertical transfer of radiative fluxes and heat fluxes but also affect horizontal advections through their effect on the atmospheric heating rate and moisture flux convergence/divergence as well as horizontal temperature gradients.
William K. M. Lau
Situated at the southern edge of the Tibetan Plateau (TP), the Hindu-Kush-Himalayas-Gangetic (HKHG) region is under the clear and present danger of climate change. Flash-flood, landslide, and debris flow caused by extreme precipitation, as well as rapidly melting glaciers, threaten the water resources and livelihood of more than 1.2 billion people living in the region. Rapid industrialization and increased populations in recent decades have resulted in severe atmospheric and environmental pollution in the region. Because of its unique topography and dense population, the HKHG is not only a major source of pollution aerosol emissions, but also a major receptor of large quantities of natural dust aerosols transported from the deserts of West Asia and the Middle East during the premonsoon and early monsoon season (April–June). The dust aerosols, combined with local emissions of light-absorbing aerosols, that is, black carbon (BC), organic carbon (OC), and mineral dust, can (a) provide additional powerful heating to the atmosphere and (b) allow more sunlight to penetrate the snow layer by darkening the snow surface. Both effects will lead to accelerated melting of snowpack and glaciers in the HKHG region, amplifying the greenhouse warming effect. In addition, these light-absorbing aerosols can interact with monsoon winds and precipitation, affecting extreme precipitation events in the HKHG, as well as weather variability and climate change over the TP and the greater Asian monsoon region.
Climate change influences the Baltic Sea ecosystem via its effects on oceanography and biogeochemistry. Sea surface temperature has been projected to increase by 2 to 4 °C until 2100 due to global warming; the changes will be more significant in the northern areas and less so in the south. The warming up will also diminish the annual sea ice cover by 57% to 71%, and ice season will be one to three months shorter than in the early 21st century, depending on latitude. A significant decrease in sea surface salinity has been projected because of an increase in rainfall and decrease of saline inflows into the Baltic Sea. The increasing surface flow has, in turn, been projected to increase leaching of nutrients from the soil to the watershed and eventually into the Baltic Sea. Also, acidification of the seawater and sea-level rise have been predicted.
Increasing seawater temperature speeds up metabolic processes and increases growth rates of many secondary producers. Species associated with sea ice, from salt brine microbes to seals, will suffer. Due to the specific salinity tolerances, species’ geographical ranges may shift by tens or hundreds of kilometres with decreasing salinity. A decrease in pH will slow down calcification of bivalve shells, and higher temperatures also alleviate establishment of non-indigenous species originating from more southern sea areas.
Many uncertainties still remain in predicting the couplings between atmosphere, oceanography and ecosystem. Especially projections of many oceanographic parameters, such as wind speeds and directions, the mean salinity level, and density stratification, are still ambiguous. Also, the effects of simultaneous changes in multiple environmental factors on species with variable preferences to temperature, salinity, and nutrient conditions are difficult to project. There is, however, enough evidence to claim that due to increasing runoff of nutrients from land and warming up of water, primary production and sedimentation of organic matter will increase; this will probably enhance anoxia and release of phosphorus from sediments. Such changes may keep the Baltic Sea in an eutrophicated state for a long time, unless strong measures to decrease nutrient runoff from land are taken.
Changes in the pelagic and benthic communities are anticipated. Benthic communities will change from marine to relatively more euryhaline communities and will suffer from hypoxic events. The projected temperature increase and salinity decline will contribute to maintain the pelagic ecosystem of the Central Baltic and the Gulf of Finland in a state dominated by cyanobacteria, flagellates, small-sized zooplankton and sprat, instead of diatoms, large marine copepods, herring, and cod.
Effects vary from area to area, however. In particular the Bothnian Sea, where hypoxia is less common and rivers carry a lot of dissolved organic carbon, primary production will probably not increase as much as in the other basins.
The coupled oceanography-biogeochemistry ecosystem models have greatly advanced our understanding of the effects of climate change on marine ecosystems. Also, studies on climate associated “regime shifts” and cascading effects from top predators to plankton have been fundamental for understanding of the response of the Baltic Sea ecosystem to anthropogenic and climatic stress. In the future, modeling efforts should be focusing on coupling of biogeochemical processes and lower trophic levels to the top predators. Also, fine resolution species distribution models should be developed and combined with 3-D modelling, to describe how the species and communities are responding to climate-induced changes in environmental variables.
Saji N. Hameed
Discovered at the very end of the 20th century, the Indian Ocean Dipole (IOD) is a mode of natural climate variability that arises out of coupled ocean–atmosphere interaction in the Indian Ocean. It is associated with some of the largest changes of ocean–atmosphere state over the equatorial Indian Ocean on interannual time scales. IOD variability is prominent during the boreal summer and fall seasons, with its maximum intensity developing at the end of the boreal-fall season. Between the peaks of its negative and positive phases, IOD manifests a markedly zonal see-saw in anomalous sea surface temperature (SST) and rainfall—leading, in its positive phase, to a pronounced cooling of the eastern equatorial Indian Ocean, and a moderate warming of the western and central equatorial Indian Ocean; this is accompanied by deficit rainfall over the eastern Indian Ocean and surplus rainfall over the western Indian Ocean. Changes in midtropospheric heating accompanying the rainfall anomalies drive wind anomalies that anomalously lift the thermocline in the equatorial eastern Indian Ocean and anomalously deepen them in the central Indian Ocean. The thermocline anomalies further modulate coastal and open-ocean upwelling, thereby influencing biological productivity and fish catches across the Indian Ocean. The hydrometeorological anomalies that accompany IOD exacerbate forest fires in Indonesia and Australia and bring floods and infectious diseases to equatorial East Africa. The coupled ocean–atmosphere instability that is responsible for generating and sustaining IOD develops on a mean state that is strongly modulated by the seasonal cycle of the Austral-Asian monsoon; this setting gives the IOD its unique character and dynamics, including a strong phase-lock to the seasonal cycle. While IOD operates independently of the El Niño and Southern Oscillation (ENSO), the proximity between the Indian and Pacific Oceans, and the existence of oceanic and atmospheric pathways, facilitate mutual interactions between these tropical climate modes.
Candice Howarth and Amelia Sharman
Labels play an important role in opinion formation, helping to actively construct perceptions and reality, and to place individuals into context with others. As a highly complex issue, climate change invites a range of different opinions and dialogues about its causes, impacts, and action required. Much work has been published in the academic literature aiming to categorize differences of opinion about climate change using labels. However, the debate about labels acts as a distraction to more fundamental and pressing issues of policy response. In addition, the undercurrent of incivility present in the climate change debate also contributes towards a hostile and unconstructive conflict.
This is an evolving area of academic enquiry. Recent work has examined how the different labels of climate change opinions are constructed, used in practice, and portrayed differently in the public and policy spheres. The growing number of categorization systems used in the climate debate are also argued to have implications for the science-policy interface, creating a polarized debate involving many different actors and interfaces.
Moving away from unhelpful use and construction of labels that lead to incivility would enable constructive and fruitful dialogue across this polarized debate. A way forward would be to explore further the role of underlying motivations and rationales as to why these different opinions about climate change come to exist in the first place. Focusing on potential overlaps in perceptions and rationales may encourage constructive discussion amongst actors previously engaged in purposefully antagonistic exchange on climate change.
Many publics remain divided about the existence and consequences of anthropogenic climate change despite scientific consensus. A popular approach to climate change communication, and science communication more generally, is the information deficit model. The deficit model assumes that gaps between scientists and the public are a result of a lack of information or knowledge. As a remedy for this gap, the deficit model is a one-way communication model where information flows from experts to publics in an effort to change individuals’ attitudes, beliefs, or behaviors. Approaches to climate change communication that reflect the deficit model include websites, social media, mobile applications, news media, documentaries and films, books, and scientific publications and technical reports. The deficit model has been highly criticized for being overly simplistic and inaccurately characterizing the relationship between knowledge, attitudes, beliefs, and behaviors, particularly for politically polarized issues like climate change. Even so, it continues to be an integral part of climate change communication research and practice. In an effort to address the inadequacies of the deficit model, scholars and practitioners often utilize alternative forms of public engagement, including the contextual model, the public engagement model, and the lay expertise model. Each approach to public engagement carries with it a unique set of opportunities and challenges. Future work in climate change communication should explore when and how to most effectively use the models of public engagement that are available.
Fred Kucharski and Muhammad Adnan Abid
The interannual variability of Indian summer monsoon is probably one of the most intensively studied phenomena in the research area of climate variability. This is because even relatively small variations of about 10% to 20% from the mean rainfall may have dramatic consequences for regional agricultural production. Forecasting such variations months in advance could help agricultural planning substantially. Unfortunately, a perfect forecast of Indian monsoon variations, like any other regional climate variations, is impossible in a long-term prediction (that is, more than 2 weeks or so in advance). The reason is that part of the atmospheric variations influencing the monsoon have an inherent predictability limit of about 2 weeks. Therefore, such predictions will always be probabilistic, and only likelihoods of droughts, excessive rains, or normal conditions may be provided. However, even such probabilistic information may still be useful for agricultural planning. In research regarding interannual Indian monsoon rainfall variations, the main focus is therefore to identify the remaining predictable component and to estimate what fraction of the total variation this component accounts for. It turns out that slowly varying (with respect to atmospheric intrinsic variability) sea-surface temperatures (SSTs) provide the dominant part of the predictable component of Indian monsoon variability. Of the predictable part arising from SSTs, it is the El Niño Southern Oscillation (ENSO) that provides the main part. This is not to say that other forcings may be neglected. Other forcings that have been identified are, for example, SST patterns in the Indian Ocean, Atlantic Ocean, and parts of the Pacific Ocean different from the traditional ENSO region, and springtime snow depth in the Himalayas, as well as aerosols. These other forcings may interact constructively or destructively with the ENSO impact and thus enhance or reduce the ENSO-induced predictable signal. This may result in decade-long changes in the connection between ENSO and the Indian monsoon. The physical mechanism for the connection between ENSO and the Indian monsoon may be understood as large-scale adjustment of atmospheric heatings and circulations to the ENSO-induced SST variations. These adjustments modify the Walker circulation and connect the rising/sinking motion in the central-eastern Pacific during a warm/cold ENSO event with sinking/rising motion in the Indian region, leading to reduced/increased rainfall.
Luis E. Hestres and Jill E. Hopke
The past two decades have transformed how interest groups, social movement organizations, and individuals engage in collective action. Meanwhile, the climate change advocacy landscape, previously dominated by well-established environmental organizations, now accommodates new ones focused exclusively on this issue. What binds these closely related trends is the rapid diffusion of communication technologies like the internet and portable devices such as smartphones and tablets. Before the diffusion of digital and mobile technologies, collective action, whether channeled through interest groups or social movement organizations, consisted of amassing and expending resources—money, staff, time, etc.—on behalf of a cause via top-down organizations. These resource expenditures often took the form of elite persuasion: media outreach, policy and scientific expertise, legal action, and lobbying.
But broad diffusion of digital technologies has enabled alternatives to this model to flourish. In some cases, digital communication technologies have simply made the collective action process faster and more cost-effective for organizations; in other cases, these same technologies now allow individuals to eschew traditional advocacy groups and instead rely on digital platforms to self-organize. New political organizations have also emerged whose scope and influence would not be possible without digital technologies. Journalism has also felt the impact of technological diffusion. Within networked environments, digital news platforms are reconfiguring traditional news production, giving rise to new paradigms of journalism. At the same time, climate change and related issues are increasingly becoming the backdrop to news stories on topics as varied as politics and international relations, science and the environment, economics and inequality, and popular culture.
Digital communication technologies have significantly reduced the barriers for collective action—a trend that in many cases has meant a reduced role for traditional brick-and-mortar advocacy organizations and their preferred strategies. This trend is already changing the types of advocacy efforts that reach decision-makers, which may help determine the policies that they are willing to consider and adopt on a range of issues—including climate change. In short, widespread adoption of digital media has fueled broad changes in both collective action and climate change advocacy. Examples of advocacy organizations and campaigns that embody this trend include 350.org, the Climate Reality Project, and the Guardian’s “Keep It in the Ground” campaign. 350.org was co-founded in 2007 by environmentalist and author Bill McKibben and several of his former students from Middlebury College in Vermont. The Climate Reality project was founded under another name by former U.S. Vice President and Nobel Prize winner Al Gore. The Guardian’s “Keep It in the Ground” fossil fuel divestment campaign, which is a partnership with 350.org and its Go Fossil Free Campaign, was launched in March 2015 at the behest of outgoing editor-in-chief Alan Rusbridger.
The strongest Indian summer monsoon (ISM) on the planet features prolonged clustered spells of wet and dry conditions often lasting for two to three weeks, known as active and break monsoons. The active and break monsoons are attributed to a quasi-periodic intraseasonal oscillation (ISO), which is an extremely important form of the ISM variability bridging weather and climate variation. The ISO over India is part of the ISO in global tropics. The latter is one of the most important meteorological phenomena discovered during the 20th century (Madden & Julian, 1971, 1972). The extreme dry and wet events are regulated by the boreal summer ISO (BSISO). The BSISO over Indian monsoon region consists of northward propagating 30–60 day and westward propagating 10–20 day modes. The “clustering” of synoptic activity was separately modulated by both the 30–60 day and 10–20 day BSISO modes in approximately equal amounts. The clustering is particularly strong when the enhancement effect from both modes acts in concert. The northward propagation of BSISO is primarily originated from the easterly vertical shear (increasing easterly winds with height) of the monsoon flows, which by interacting with the BSISO convective system can generate boundary layer convergence to the north of the convective system that promotes its northward movement. The BSISO-ocean interaction through wind-evaporation feedback and cloud-radiation feedback can also contribute to the northward propagation of BSISO from the equator. The 10–20 day oscillation is primarily produced by convectively coupled Rossby waves modified by the monsoon mean flows. Using coupled general circulation models (GCMs) for ISO prediction is an important advance in subseasonal forecasts. The major modes of ISO over Indian monsoon region are potentially predictable up to 40–45 days as estimated by multiple GCM ensemble hindcast experiments. The current dynamical models’ prediction skills for the large initial amplitude cases are approximately 20–25 days, but the prediction of developing BSISO disturbance is much more difficult than the prediction of the mature BSISO disturbances. This article provides a synthesis of our current knowledge on the observed spatial and temporal structure of the ISO over India and the important physical processes through which the BSISO regulates the ISM active-break cycles and severe weather events. Our present capability and shortcomings in simulating and predicting the monsoon ISO and outstanding issues are also discussed.
Media research has historically concentrated on the many uncertainties in climate science either as a dominant discourse in media treatments measured by various forms of quantitative and qualitative content analysis or as the presence of skepticism, in its various manifestations, in political discourse and media coverage. More research is needed to assess the drivers of such skepticism in the media, the changing nature of skeptical discourse in some countries, and important country differences as to the prevalence of skepticism in political debate and media coverage. For example, why are challenges to mainstream climate science common in some Anglophone countries such as the United Kingdom, the United States, and Australia but not in other Western nations? As the revolution in news consumption via new players and platforms causes an increasingly fragmented media landscape, there are significant gaps in understanding where, why, and how skepticism appears. In particular, we do not know enough about the ways new media players depict the uncertainties around climate science and how this may differ from previous coverage in traditional and mainstream news media. We also do not know how their emphasis on visual content affects audience understanding of climate change.
Yongkang Xue, Yaoming Ma, and Qian Li
The Tibetan Plateau (TP) is the largest and highest plateau on Earth. Due to its elevation, it receives much more downward shortwave radiation than other areas, which results in very strong diurnal and seasonal changes of the surface energy components and other meteorological variables, such as surface temperature and the convective atmospheric boundary layer. With such unique land process conditions on a distinct geomorphic unit, the TP has been identified as having the strongest land/atmosphere interactions in the mid-latitudes.
Three major TP land/atmosphere interaction issues are presented in this article: (1) Scientists have long been aware of the role of the TP in atmospheric circulation. The view that the TP’s thermal and dynamic forcing drives the Asian monsoon has been prevalent in the literature for decades. In addition to the TP’s topographic effect, diagnostic and modeling studies have shown that the TP provides a huge, elevated heat source to the middle troposphere, and that the sensible heat pump plays a major role in the regional climate and in the formation of the Asian monsoon. Recent modeling studies, however, suggest that the south and west slopes of the Himalayas produce a strong monsoon by insulating warm and moist tropical air from the cold and dry extratropics, so the TP heat source cannot be considered as a factor for driving the Indian monsoon. The climate models’ shortcomings have been speculated to cause the discrepancies/controversies in the modeling results in this aspect. (2) The TP snow cover and Asian monsoon relationship is considered as another hot topic in TP land/atmosphere interaction studies and was proposed as early as 1884. Using ground measurements and remote sensing data available since the 1970s, a number of studies have confirmed the empirical relationship between TP snow cover and the Asian monsoon, albeit sometimes with different signs. Sensitivity studies using numerical modeling have also demonstrated the effects of snow on the monsoon but were normally tested with specified extreme snow cover conditions. There are also controversies regarding the possible mechanisms through which snow affects the monsoon. Currently, snow is no longer a factor in the statistic prediction model for the Indian monsoon prediction in the Indian Meteorological Department. These controversial issues indicate the necessity of having measurements that are more comprehensive over the TP to better understand the nature of the TP land/atmosphere interactions and evaluate the model-produced results. (3) The TP is one of the major areas in China greatly affected by land degradation due to both natural processes and anthropogenic activities. Preliminary modeling studies have been conducted to assess its possible impact on climate and regional hydrology. Assessments using global and regional models with more realistic TP land degradation data are imperative.
Due to high elevation and harsh climate conditions, measurements over the TP used to be sparse. Fortunately, since the 1990s, state-of-the-art observational long-term station networks in the TP and neighboring regions have been established. Four large field experiments since 1996, among many observational activities, are presented in this article. These experiments should greatly help further research on TP land/atmosphere interactions.
Jonathan Holmes and Philipp Hoelzmann
From the end of the last glacial stage until the mid-Holocene, large areas of arid and semi-arid North Africa were much wetter than present, during the interval that is known as the African Humid Period (AHP). During this time, large areas were characterized by a marked increase in precipitation, an expansion of lakes, river systems, and wetlands, and the spread of grassland, shrub land, and woodland vegetation into areas that are currently much drier. Simulations with climate models indicate that the AHP was the result of orbitally forced increase in northern hemisphere summer insolation, which caused the intensification and northward expansion of the boreal summer monsoon. However, feedbacks from ocean circulation, land-surface cover, and greenhouse gases were probably also important.
Lake basins and their sediment archives have provided important information about climate during the AHP, including the overall increases in precipitation and in rates, trajectories, and spatial variations in change at the beginning and the end of the interval. The general pattern is one of apparently synchronous onset of the AHP at the start of the Bølling-Allerød interstadial around 14,700 years ago, although wet conditions were interrupted by aridity during the Younger Dryas stadial. Wetter conditions returned at the start of the Holocene around 11,700 years ago covering much of North Africa and extended into parts of the southern hemisphere, including southeastern Equatorial Africa. During this time, the expansion of lakes and of grassland or shrub land vegetation over the area that is now the Sahara desert, was especially marked. Increasing aridity through the mid-Holocene, associated with a reduction in northern hemisphere summer insolation, brought about the end of the AHP by around 5000–4000 years before present. The degree to which this end was abrupt or gradual and geographically synchronous or time transgressive, remains open to debate. Taken as a whole, the lake sediment records do not support rapid and synchronous declines in precipitation and vegetation across the whole of North Africa, as some model experiments and other palaeoclimate archives have suggested. Lake sediments from basins that desiccated during the mid-Holocene may have been deflated, thus providing a misleading picture of rapid change. Moreover, different proxies of climate or environment may respond in contrasting ways to the same changes in climate. Despite this, there is evidence of rapid (within a few hundred years) termination to the AHP in some regions, with clear signs of a time-transgressive response both north to south and east to west, pointing to complex controls over the mid-Holocene drying of North Africa.
Michael Faure and Marjan Peeters
In view of the need to curb greenhouse gases, the question arises as to the functions of liability in providing effective incentives for emitters in order to change their behavior. Liability for emitting greenhouse gases exists (or can exist) in the area of public law and private law and can be subdivided into international, administrative, and criminal liability (public law liabilities) and tort law liability (private law liability). Actions for holding individual and legal persons (such as states, authorities, and companies) liable can, depending on the specific jurisdiction, be triggered by citizens but also by legal persons, such as authorities, companies, and non-governmental organizations (NGOs), particularly environmental NGOs. The central question in this article is how climate liability is arranged under public law and whether there would be any role for climate liability to play under private law, thereby applying a legal and economic methodology. That so-called law and economics doctrine is a useful approach as it has given a lot of attention, for example, to the different functions of specific legal instruments (more particularly regulation, including taxation and emissions trading and tort law liability) for mitigating greenhouse gases. Meanwhile, in practice, various examples can be identified whereby tort law liability is used as a complement to greenhouse gas regulation. This specific use of tort liability is analyzed in the light of the law and economics literature, thereby pointing at prospects but also at remaining core questions. The success of tort law actions will most likely greatly depend on the (lack of) ambition vested into the emissions regulations at international and national levels. One of the exciting questions for the near future is to what extent judges feel able to step into the regulation of the climate change problem, in an ex ante way. The most difficult cases are obviously those where a regulatory system concerning greenhouse gas mitigation has been put in place and where the court system is strong, but where particular groups consider the regulations to be insufficient.